In this photo provided by ThinkFilm, Dan, a poet (Heath Ledger) falls in love with an art student Candy (Abbie Cornish) who gravitates to his bohemian lifestyle -- and his love of heroin in "Candy." (AP Photo/ThinkFilm)

In "Candy," his first film since "Brokeback Mountain," Heath Ledger returns to Australia to speak in his natural accent and display an exuberance that also comes naturally but was dampened to play a taciturn cowboy. The energy Ledger projects as Dan, a part-time poet living on the edge, becomes scary when fueled by heroin.

For all its depiction of a descent into drug addiction, "Candy" is filled with surprisingly sweet moments and goes down more easily than seems possible given the subject matter.

As in "Leaving Las Vegas," there's a love story to divert you. Dan begins a passionate romance with a painter, Candy (Abbie Cornish, an Australian actress touted as the next Nicole Kidman as much for her talent as her luscious looks). They're kids at heart, a point emphasized in an exhilarating opening scene of the two whirling around and around on an amusement park ride. They look as if they never want to stop. Watching from above is Dan's mentor, Casper (Geoffrey Rush), part protector, part drug supplier.

Although director Neil Armfield's career has mostly been in the Sydney theater, he has an intuitive cinematic eye, capturing the barrenness of Australia's countryside. His camera picks up reflections in windowpanes of cars and mirrors. During a low point after Candy switches from sniffing heroin to shooting it, she runs a hand down her devastated mirror image.

"Candy" is divided into three segments. Signs that flash on the screen alerting you to where you are in a story can be annoying, as if the audience won't figure it out otherwise. But in this instance, they serve a purpose. The section labeled "Heaven" offers the promise of joy. Dan and Candy lust after each other, and drugs only increase their passion. Heath and Cornish bring eye-popping realism to their sex scenes.

In the second part, the couple falls to "Earth." Candy stops painting and spends her time prostituting herself for drug and rent money. Her blond hair is dirty. Casper lurks in the background, a ready source of cash or heroin, which, as a chemistry professor, he cooks up in his lab. Rush plays him with great flamboyance but also a touch of sadness appropriate to his ambiguous role in Dan and Candy's lives.

Armfield and co-screenwriter Luke Davies (on whose semiautobiographical novel the film is based) appear to have calibrated how much despair they can get away with before an injection of humor is required. Eager to help with the family finances, Dan considers becoming a male hooker but decides he would be "hopeless with the gay stuff" -- a line that whether intentionally or not will get a laugh out of anyone who saw "Brokeback Mountain."

Ledger is mesmerizing in a scene where Dan pulls off a white-collar crime by going to a bank with a stolen ID and charming a cashier into giving him more than $2,000. Hyped up, he keeps repeating to himself, "I'm rolling," like a mantra.

Even the final episode, "Hell," isn't as hellish as it sounds, thanks to the filmmakers' unerring sense of their limits. "Candy" is hardly a feel-good movie, but you'll leave it feeling not nearly as depressed as you might think.